<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        .box1 {
            width: 500px;
            height: 500px;
            background-color: red;
           
        }
       .box2 {
           width: 200px;
            height: 200px;
            background-color: rgb(0, 255, 76);
       }
       .box3{
            width: 100px;
            height: 100px;
            background-color: blue
       }

      
    </style>
</head>
<body>
    <div class="box1">
        <div class="box2">
            <div class="box3"></div>
        </div>
    </div>
</body>
</html>